Currently, signage or information display using a large-screen display device has various uses, and a system that enables large-screen display with a single display panel, or a system in which a plurality of display panels are positioned in a matrix to constitute a multi-display having a large screen and to perform display is increasingly used.
A display using a liquid crystal panel is constituted by a liquid crystal panel formed by filling a gap between a pair of glass substrates with a liquid crystal substance, and backlights positioned on the back of the liquid crystal panel, and displays an image by driving the liquid crystal panel in accordance with an image signal fed from an external device, such as a PC (personal computer) or a playback device.
In a liquid crystal display device, a gate driver and a source driver are mounted as a driving circuit for the liquid crystal panel. The gate driver is connected to the gate of each transistor that drives a corresponding pixel of the liquid crystal panel, and the source driver is connected to the source of each transistor. The gate driver performs on/off control on each transistor on the basis of an input image signal, the source driver applies, to each transistor that is turned on, a voltage (an input level for the liquid crystal panel) that corresponds to the image signal to thereby change the light transmittance, which is determined on the basis of the electro-optic properties of the liquid crystal substance. As a result, the liquid crystal display device can represent gradations by controlling, on a per pixel basis, the amount of light that is emitted from the backlights and passes through the liquid crystal panel.
The electro-optic properties of the liquid crystal substance is determined on the basis of the gap, namely, the cell gap, between the glass substrates, which is filled with the liquid crystal substance. However, due to variations in manufacture or other factors, pixels having a small cell gap and pixels having a large cell gap relative to the design value are present in a mixed manner, the light transmittance of each pixel deviates from the design value, desired gradation properties are not achieved, and luminance unevenness or color unevenness occurs in the liquid crystal panel. In the liquid crystal display device, luminance unevenness also occurs due to variations or fluctuations in the properties among the plurality of light sources used for the backlights.
Accordingly, for liquid crystal display devices, a calibration process for creating a luminance adjustment table for correcting luminance unevenness and a calibration process for creating a chromaticity adjustment table for correcting chromaticity unevenness from data obtained by capturing images of displayed test images are currently performed to correct unevenness of image data by using these adjustment tables.